The present invention relates to a color filter and a liquid crystal display and in particular to a liquid crystal display excellent in display qualities and a color filter using the same.
In recent years, a color liquid crystal display attracts attention as a flat display. As one example of the color liquid crystal display, there is a transmission-type liquid crystal display in which a color filer having a black matrix, colored layers consisting of a plurality of colors (usually the 3 primary colors of red (R), green (G) and blue (B)), a common transparent electrode layer and an orientation layer is opposed via a predetermined gap to an opposite electrode substrate having a thin film transistor (TFT element), a picture element electrode and an orientation layer, wherein a liquid crystal layer is formed by injecting a liquid crystal material into said gap. Further, there is also a reflection-type liquid crystal display provided with a reflective layer between the color filter substrate and the colored layers described above.
Such color liquid crystal displays are liable to display insufficiencies upon a change in orientation of a liquid crystal caused by insufficient orientation of the liquid crystal, by a change in voltage applied to the liquid crystal or by varying voltage on the display. These display insufficiencies include the following sticking and white stain.
The sticking is a phenomenon in which uneven display occurs and continues for a long time in the case where a certain voltage is applied to the same picture element for a predetermined time and then reduced or stopped, and this occurs due to a difference in the light transmittance of the picture element from the transmittance of surrounding picture elements to which the voltage was not applied. In the sticking phenomenon in a normally white panel, picture elements to which a voltage was applied for a predetermined time seem darker than in surrounding picture elements. The reason for such sticking phenomenon is possibly that ionic materials adhere to the electrode during application of voltage, and after the voltage is relieved, the ionic materials are still adsorbed onto the electrode, and the voltage attributable to these ionic materials continues to act on the liquid crystal.
White stain is a phenomenon in which uneven display is observed when a black picture is indicated by applying a voltage, and this occurs because the transmittance of a part of the display does not become zero. The reason for this phenomenon may be attributable to the fact that whereas the voltage applied across the electrodes should be kept constant, the voltage across the electrodes is lowered when ionic materials are present in the liquid crystal and these are transferred between the electrodes, that is, an electric current flows between the electrodes.
It is considered that ionic materials causing the phenomena of display insufficiencies described above are easily transferred to the liquid crystal layer without being retained in the electrode. There are a large number of possible sources generating such ionic materials, and for preventing these display insufficiencies, impurities contained in chemical liquids used in the process, the air, purified water etc. and dust from devices, human body etc. are controlled during the process, and the process conditions are optimized. Further, impurities such as residues are removed by washing of the surface of the color filter or the opposite electrode substrate, by UV irradiation, or by polishing the surface thereof in the process.
The phenomena of display insufficiencies hardly occur due to these measures, but can still occur frequently under severe display conditions such as display for a long time or at high temperatures under high humidity.
The present invention was made in view of the circumstance described above, and an object of the present invention is to provide a color filter for reliably preventing the liquid crystal layer from being contaminated with ionic materials, as well as a liquid crystal display excellent in display qualities.
The resin member brought into contact with the liquid crystal layer in the liquid crystal display is considered to be one source generating ionic materials, and the present invention was made by paying attention to the voltage holding ratio and the residual DC (xcex94E) in the liquid crystal subjected to the treatment for extraction of impurities from the resin member, as characteristics correlative to display insufficiencies caused by ionic materials transferred from the resin member to the liquid crystal layer.
To achieve the object described above, a color filter of a first aspect of the invention is constituted such that it comprises a substrate, a resin colored layer consisting of a plurality of colors formed in a predetermined pattern on the substrate, and a common transparent electrode layer, said resin colored layer bringing about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A color filter of a second aspect of the invention is constituted such that it comprises a substrate, a colored layer consisting of a plurality of colors formed in a predetermined pattern on the substrate, a transparent resin protective layer formed to cover at least the colored layer, and a common transparent electrode layer, said resin protective layer bringing about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A color filter of a third aspect of the invention is constituted such that the color filter of the second aspect further comprises transparent resin pillar-shaped convexes formed in a plurality of predetermined regions on the substrate and protruded from the resin protective layer, said resin pillar-shaped convex bringing about a voltage holding ratio of 80 or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A liquid crystal display of the first aspect of the invention is constituted such that it comprises a color filter and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, said color filter being any of the color filters described above.
A liquid crystal display of the second aspect of the invention is constituted such that it comprises a color filter and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, wherein the color filter is any of the color filters described above, the opposite electrode substrate comprises a semiconductor driving element provided with a resin shading layer, and the resin shading layer brings about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A liquid crystal display of the third aspect of the invention is constituted such that it comprises a color filter and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, wherein the color filter is the color filter of the first or second aspect of the invention described above, the opposite electrode substrate comprises a semiconductor driving element provided with resin pillar-shaped convexes, and the resin pillar-shaped convexes bring about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A liquid crystal display of the fourth aspect of the invention is constituted such it comprises a common electrode substrate and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, wherein the common electrode substrate comprises a common transparent electrode layer on the substrate, the opposite electrode substrate comprises semiconductor driving elements and a resin colored layer consisting of a plurality of colors formed in a predetermined pattern corresponding to each of the semiconductor driving elements, and the resin colored layer brings about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A liquid crystal display in the fifth aspect of the invention is constituted such that it comprises a color filter and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, wherein the color filter comprises a substrate and a reflective layer, a resin colored layer consisting of a plurality of colors and a common transparent electrode layer laminated in this order over the substrate, and the resin colored layer brings about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
A liquid crystal display in the sixth aspect of the invention is constituted such that it comprises a common electrode substrate and an opposite electrode substrate opposite to each other to provide a gap via a sealing member and a liquid crystal layer sealed in the gap, wherein the common electrode substrate comprises a common transparent electrode layer on the substrate, the opposite electrode substrate comprises a substrate, a driving element layer, a reflective electrode layer, and a resin colored layer consisting of a plurality of colors laminated in this order over the substrate, and the resin colored layer brings about a voltage holding ratio of 80% or more and a residual DC (xcex94E) of 0.5 V or less in a liquid crystal subjected to treatment for extraction of impurities.
As described in detail above, the rein members constituting the color filter of the present invention, which are brought directly into contact with the liquid crystal layer or positioned nearest to the liquid crystal layer via a film, are those making a voltage holding ratio and a residual DC (xcex94E) in a specific range in the liquid crystal subjected to the treatment for extraction of impurities from the resin members, or the resin members which in the liquid crystal display, are brought directly into contact with the liquid crystal layer or positioned nearest to the liquid crystal layer via a film, are those making a voltage holding ratio and a residual DC (xcex94E) in a specific range in the liquid crystal subjected to the treatment for extraction of impurities from the resin members, so that display insufficiencies such as sticking and white stain can be prevented even under severe display conditions such as display for a long time at high temperature and under high humidity, and the liquid crystal display excellent in display qualities is thus realized.